The present invention relates generally to a fiber optic connector and, more particularly, to a fiber optic connector employing a substantially matching index of refraction material between the mating faces of the optical fibers in the connector.
The present invention will be described specifically in connection with a single fiber optical fiber connector, although it will be appreciated that the invention could also be applicable to fiber bundle connectors. Regardless of the fiber alignment mechanism utilized in a single fiber demountable connector, an optical loss will occur at the interface of the opposing fibers. This loss is due to the reflections at the end faces of the fibers and is a function of the index of refraction differences of the fiber cores and the air between the two fibers. This loss is commonly known as the Fresnel loss and is theoretically equivalent to 0.32 dB.
In order to eliminate the Fresnel loss, it is known in the art that an index of refraction matched material may be introduced between the mating faces of the optical fibers in the connector. U.S. Pat. No. 3,455,625 to Brumley discloses that such material may be liquid or grease-like. It is commonly believed in the industry that there are serious disadvantages to the use of liquid materials, one of which is the inability to perform repeated matings and dematings of the connector parts without loss of the liquid. Brumley also teaches the use of a solid silicone elastomer disc between the mating faces of optical fibers. Such disc, however, is relatively thick and, therefore, causes optical power losses. U.S. Pat. No. 3,984,174 to Landgreen teaches the use of a clear silicone rubber coating over the end of a fiber optic bundle terminal. Landgreen discloses that the thickness of the coating is about 0.002 inch. With two mating terminals provided with such coatings, a 0.004 inch gap will occur between the end faces of the fiber bundles in the terminals which still results in a minor loss of optical transmission through the connector.
It is the object of the present invention to provide a very thin, but solid, substantially indexed matching element between the mating faces of optical fibers in a connector which causes less optical power losses than the solid indexed matched elements of the prior art, yet without the risk of loss of the material upon repeated matings and dematings of the connector halves.